how the sonar works ?

Sonar is a very important naval equipment, and it has received great attention from all countries with the using of underwater weapons such as submarines. Here, we don't discuss a specific equipment, nor do we involve too many mathematical concepts. Instead, we start with a simple physical principle and give a brief introduction to the sonar under the water.

The current sonar is mainly divided into two categories, active sonar and passive sonar. Active sonar work is similar to radar, or more like a bat, after receiving a sound wave, piezoelectric ceramics receives a reflected signal. Since the principle is similar, the question is coming, why not move the radar directly to the water? Quite simply, radar-dependent electromagnetic waves are heavily attenuated underwater, and are simply not sufficient for long-range detection. The sound wave is generated by the vibration of the object, and the distance traveled in the water is very far. A huge explosion in the water can be heard in the places thousands of kilometers away.

There are two main types of such piezo ceramic tubes components. The magnetic field or the electric field can be used to deform the object. Here we focus on the principle of using an electric field to control the deformation and vibration of the object, namely the inverse piezoelectric effect and the piezoelectric effect.

Then the inverse piezoelectric effect of piezo cylinder tube materials is the electric field to control the deformation of the object. When the wires are connected to the upper and lower ends of the piezoelectric body and a voltage is applied, the object is elongated or shortened in the direction of the electric field. If the loading speed of the electric field is increasing, that is, the frequency is increased, the deformation of the object can be accelerated to generate vibration and emit sound waves. Together with other supporting equipment, it becomes the sound source of active sonar.

Then the inverse piezoelectric effect is the electric field to control the deformation of the object. When the wires are connected to the upper and lower ends of the piezoelectric body and a voltage is applied, the object is elongated or shortened in the direction of the electric field. If the loading speed of the electric field is increasing, that is, the frequency is increasing, the deformation of the object can be accelerated to generate vibration and emit sound waves. Together with other supporting equipment, it becomes the sound source of active sonar.

In the crystal structure of barium titanate or PZT, the center positions of the positive and negative charges coincide, and the dipole is generated when the temperature of the positive and negative charges no longer coincides after the temperature is lowered to a certain value. This dipole phenomenon is brought about spontaneous polarization. In a ceramic body, regions of the same spontaneous polarization orientation generate domains again, and the domains are flipped under an external electric field to maintain the same direction as the electric field. During this period, if the angle of the domain steering is not 180 degrees, then this rotation will bring about a change in the shape of the pzt4 piezo ceramic tubular transducer, that is, the strain under a large electric field. If it is an alternating electric field, hysteresis will occur in a loading cycle. Therefore, in practical applications, the large electric field is pre-polarized, and the domains are oriented in one direction. After that, the direction of the electric field should not be changed as much as possible to avoid hysteresis and depolarization. Of course, some electronic storage devices are excluded. After solving the problem of generating sound waves and receiving sound waves, in order to enhance performance, the units of the sonar are generally in the form of an array, which is matched with other devices such as phase shifters and the like.Implement a scan of a specific area. Large arrays are often spherical or column-shaped, so large that the submarine's torpedo tubes are given way. The warship or the rear of the submarine often forms a blind spot due to the propulsion system, so the towed sonar is far from the noise area of the stern.